PATHOPHYSIOLOGICAL ROLE OF CHANGING ATRIAL SIZE AND PRESSURE IN MODULATION OF ATRIAL-NATRIURETIC-FACTOR DURING EVOLVING EXPERIMENTAL HEART-FAILURE

Study objective - The aim was to study the interactions between pulmonary capillary wedge pressure (an estimate of left atrial pressure), left atrial dimension, and atrial natriuretic factor during evolving heart failure.Design - Sequential simultaneous measurements of haemodynamic variables, left atrial dimension, and plasma atrial natriuretic factor concentrations were obtained during evolving experimental pacing induced heart failure.Experimental material - Eight male mongrel dogs were paced (250 beats·min-1) to severe heart failure over 4.9(SD 1.8) weeks.Measurements and results - The development of heart failure was characterised by a progressive increase in pulmonary capillary wedge pressure and left atrial cross sectional area, from 5.6(1.3) mm Hg and 7.9(1.2) cm2 respectively at control, to 25.3(4.9) mm Hg and 14.2(2.5) cm2 respectively (both p<0.01) at severe heart failure. In contrast to the progressive increase in pulmonary capillary wedge pressure and left atrial area, plasma atrial natriuretic factor concentration increased from 98(51) ng·litre-1 at control to a peak of 422(110) ng·litre-1 (p<0.01) at 1 week, then plateaued and reached 354(108) ng·litre-1 at severe heart failure (p<0.05 v control). Plasma atrial natriuretic factor correlated with pulmonary capillary wedge pressure and left atrial area at 1 week (r = 0.73, r = 0.71 respectively, both p<0.0l), but not at the time of severe heart failure.Conclusion - The divergent time course of the changes in plasma atrial natriuretic factor concentration, pulmonary capillary wedge pressure, and left atrial dimension suggests that in this model, the release of atrial natriuretic factor becomes attenuated as severe heart failure develops.